The present invention relates to a semiconductor integrated circuit apparatus, and more particularly to a fuse-latch unit, which comprises fuse circuits and latch output circuits connected to the fuses for outputting the data the fuse circuits stores.
The integration density of LSIs keeps increasing. Integration technology is advancing in the designing of memory devices such as DRAM, SRAM and flash EEPROM and various semiconductor integrated circuits each including a memory.
Programming by using fuses is performed in semiconductor integrated circuits to select redundancy circuits, to adjust internal power supply and circuit operation minutely, and to select circuit functions. The programming is effected to reduce the difference in operating characteristics between the circuits, to enhance the yield of the product, to enable the circuits to function over broad ranges. More precisely, programming by use of fuses is carried out after a semiconductor IC chip has been manufactured. The programming is performed to compensate for the difference between the design and actual characteristic of the IC chip, to replace defective word lines and bit lines with redundancy word lines and bit lines. Thus, the programming by use of fuses determines the function and electrical characteristics of the IC chip.
FIG. 1 is a plan view showing the layout of a fuse-latch unit comprising fuses FUSE and latch output circuits LCHO connected to the fuses FUSE, respectively. Selected ones of the fuses FUSE are cut to accomplish programming. The fuse-latch unit is incorporated in a semiconductor IC, along with other components. The semiconductor IC is incorporated in a package, forming a semiconductor IC chip. The fuse-latch unit functions as a source of control signals that correct and adjust the operation of the semiconductor IC. The fuses FUSE, including those already cut, store read-only data from which the control signals will be generated. The latch output circuits LCHO cooperate to read the read-only data.
The higher the integration density of the semiconductor IC, the more fuses and the more latch output circuits the semiconductor IC needs to have. The greater the number of fuses and latch output circuits, the more longer the pitch of the latch output circuits than the pitch of the fuses.
Some of the fuses FUSE provided in the semiconductor IC are cut or blown by means of a laser cutter. The laser cutter has advanced in terms of performance. It can cut selected ones of fuses even if the fuses FUSE are arranged at a pitch much shorter than before. It is very difficult, however, to arrange the latch output circuits LCHO at so short a pitch as the fuses FUSE. More specifically, the pitch Y of the latch output circuits LCHO cannot be reduced further though the pitch X of the fuses FUSE can be decreased.
Hence, the minimum pitch X of the fuses FUSE is inevitably equal to the pitch Y of the latch output circuits LCHO as is illustrated in FIG. 1, though it can be reduced. As a consequence, dead spaces DSP are provided between the fuses FUSE.
The trend is that the storage capacity and size of a fuse-latch unit of the type described above is increasing. Therefore, the fuse-latch unit requires fuses and latch output circuits in greater numbers. The fuses are usually arranged in a certain region in the semiconductor IC chip in order to enhance the efficiency of blowing some of the fuses for data programming.
If the fuses and the latch output circuits are arranged at the same pitch as shown in FIG. 1, the dead spaces DSP between the fuses are left unused and, moreover, the size of the fuse-latch unit cannot be reduced in the direction the fuses are arranged. Consequently, the fuse-latch unit decreases the area in which the other components of the semiconductor IC. This makes a problem in size reduction of the semiconductor IC.